1. Field of the Invention
Aspects of the present invention relate generally to an operational amplifier, and more particularly to setting the quiescent current in a rail-to-rail output stage of an operational amplifier.
2. Description of Related Art
Operational amplifiers (“op-amps”) are widely known and used electronic devices that may be employed in a variety of applications. Generally, an op-amp is a DC-coupled high gain electronic voltage amplifier with differential inputs and a single output. As op-amps trend toward using lower supply voltages, the ability for the op-amp to swing from rail to rail has increased in importance. By being able to swing from rail to rail, the op-amp may use its full or close to its full voltage range on output and input. Rail-to-rail op-amps may be suited for low voltage applications.
However, random variations in the quiescent current flowing in the op-amp may occur due to manufacturing processes. These variations may affect the ability to properly bias an output transistor to control and maintain the desired quiescent current in a circuit.
Therefore, it may be desirable to provide a circuit arrangement that precisely sets the quiescent current in a rail-to-rail output stage of the op-amp.